Considering who we have had in the WH for the past 6 1/2 years, I’d say voters can be stupid. That applies, of course, only to liberals.
I'm going to offer a different view here: The voters in fact knew what they were doing, or WHAT THEY WANTED TO DO, when they put in Zero. They wanted to make a giant statement that "No, we're not racist. See? We'll elect a black man." And they completely ignored his Marxist doctrines, because to them it wasn't about his policies, it was only about his skin.
I think you can prove that with polls about almost every one of his policies, about the direction of the country, but few voters want to attach that to ZEro for the reasons mentioned above. That's why he continues to get away with it.
I think---hope---that they will view this election as a way to say, "OK, whew, we did that. Now let's get back to things that matter."